MAX038 Function generator chip

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spindrah

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I'm making a function generator with the MAX038 chip

it is supposed to give 2v out p-p
But I'm getting +1 to just under -1
and it has small jumps on the negative side from 50hz to 100Khz(see picture)

at 2Mhz the jumps are gone but it still doesn't go to -1v

i would appreciate any help with this
thanks
 

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The load resistance is too low and/or the power supply voltages are too low or are dropping.
 
audioguru said:
The load resistance is too low and/or the power supply voltages are too low or are dropping.
Click to expand...

thanks for the reply

i only have the scope on the output,is that ok?

for power i have 2 - 9volts with a 7805 giving me 4.97v
and a 7905 giving -4.96
 
spindrah said:
I'm making a function generator with the MAX038 chip

it is supposed to give 2v out p-p
But I'm getting +1 to just under -1
Click to expand...

+1 to -1 is 2Vp-p. It meets its spec's of 1.9Vp-p to 2.1Vp-p.

it has small jumps on the negative side from 50hz to 100Khz
Click to expand...
like other function generators its sinewave distortion is about 1% which isn't very good. It is normal for a function generator. Its sinewave shaper just chops up its triangle wave.
 
In the datasheet it says "output p-p symmetry" +or- 4mV
but the output does not look symmetrical to me

wouldn't it need to be (.95 to -.95) or (1.05 to -1.05) to be symmetrical and within the 1.9 to 2.1 range?


Or am i reading the wrong thing into it?

thanks for the help
 
Its sinewave symmetry might be better if you adjust its duty-cycle.

Are you using little 9V batteries? The MAX038 has a pretty high operating current and their voltage would quickly drop lower than the 7.5V minimum input voltage of the 7805 and 7809 regulators. Then your 5V supplies won't be regulated anymore, affecting output level and symmetry.
 
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